Hello Guys,

I hope to develop my sketch interactivelly and tried jython(http://www.jython.org/Project/).
It's very easy to use jython with proce55ing, but I found it's not so interactive environment.
When I modified my subclass of PApplet, I should close running PApplet and launch it again because I have no way to re-define class.

I got the idea to make PApplet.draw() method event-driven. My idea is to define new Event(PDrawEvent) and treat PApplet as an EventListener. By this small patch and jython, I could modify code without closing PApplet window.

I hope you'll be interested in this patch.


Session jython with Pached PApplet sample:
('>>>' is jython prompt. create PApplet instance, and add modify it's behaviour without close window.)

>>> from processing.core import PApplet
>>> p=PApplet()
>>> from java.awt import Frame
>>> f=Frame(size=(200,200))
>>> f.add(p)
processing.core.PApplet[panel1,0,0,0x0,invalid,layout=java.awt.FlowLayout]
>>> f.visible = 1
>>> def fn(evt):
...
p.line(0, 0, p.random(p.width), p.random(p.height))
...
>>> p.doDraw = fn
>>> p.init()
>>> p.stop()
>>> def gn(evt):
...
p.line(p.random(p.width), p.random(p.height), p.random(p.width), p.random(p.height))
...
>>> p.doDraw = gn
>>> p.init()

my patch to PApplet:

--- PApplet.java
2008-09-07 21:41:11.000000000 +0900
+++ PApplet.java.new
2008-09-07 21:41:56.000000000 +0900
@@ -156,7 +156,7 @@
 */
public class PApplet extends Applet
  implements PConstants, Runnable,
-             MouseListener, MouseMotionListener, KeyListener, FocusListener
+             MouseListener, MouseMotionListener, KeyListener, FocusListener,Serializable
{
  /**
   * Full name of the Java version (i.e. 1.5.0_11).
@@ -527,6 +527,28 @@
  // for 0116, the CRUSTY_THREADS are being disabled to fix lots of bugs.
  static final boolean CRUSTY_THREADS = false; //true;

+  // to avoid the tight coupling between PApplet class and draw() method,
+  // add PDrawEvent/PDrawEventListener.
+  private PDrawEventListener pdrawEventListener = null;
+  
+  // uni-cast style event listener.
+  public void addPDrawEventListener(PDrawEventListener listener) throws TooManyListenersException {
+    if (pdrawEventListener != null) {
+      throw new TooManyListenersException("PDrawEventListener is uni cast.");
+    }
+    pdrawEventListener = listener;
+  }
+  
+  public void removePDrawEventListener(PDrawEventListener listener) {
+    pdrawEventListener = null;
+  }
+
+  public void firePDrawEventListener(PDrawEvent evt) {
+    // if no EventListener registered, do nothing.
+    if (pdrawEventListener != null) {
+      pdrawEventListener.doDraw(evt);
+    }
+  }

  public void init() {
//    println("Calling init()");
@@ -888,7 +910,9 @@
  public void draw() {
    // if no draw method, then shut things down
    //System.out.println("no draw method, goodbye");
-    finished = true;
+    // fire PDrawEvent
+    firePDrawEventListener(new PDrawEvent(this));
+    //    finished = true;
  }


PDrawEvent.java (new class):
----
package processing.core;

import java.util.EventObject;
import java.io.Serializable;

public class PDrawEvent extends EventObject implements Serializable{
   public PDrawEvent (Object source) {

super(source);
   }
}
----
PDrawEventListener.java (new class):
----
package processing.core;

import java.util.EventListener;

public interface PDrawEventListener extends EventListener {
   public void doDraw(PDrawEvent evt);
}
----

fry wrote on Sep 8^th, 2008, 4:11am:


Thank you for your reply, but I feel in sense of embarrassment.

I'm sorry for my misleading statement,  but I don't want to redraw. It seems that redraw method just redraw..
I want to replace draw method in run time without destroy PApplet instance.  
I think it is impossible to replace draw method with original PApplet, because draw method is bind to the class tightly. I think it is possible only if I create new instance.

(I'm sorry I'm not good at English ..)